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Conventional Practices in Section view drawing

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Chapter 8
Convention Practice
in Orthographic
Writing
TOPICS
пЃ¬
Definition
пЃ¬
Purposes
пЃ¬
Types of conventions
- Alternate position of side view
- Incompleted view
- Aligned view
- Enlarged view
- Non-existing intersection line
- Cylinder intersection
DEFINITION
Convention is a commonly accepted practices
which disregard some strict rules of orthographic
projection.
Object
Multiview
representation
Projection’ s Disregard
some rules
rules
Convention
practices
More readable
multiview
representation
EXAMPLE : Already met convention practice
Front view
Using a dash line for
representing the hidden edge.
CONVENTION
PRACTICE
PURPOSES
To improve the clarity of a drawing.
To facilitate the dimensioning.
To reduce the drafting effort.
To save or efficiently use a drawing
space.
TYPES OF
CONVENTION PRACTICE
1. Alternate position of side view
2. Incompleted view
2.1 Incompleted side view
2.2 Partial view
2.3 Half view
2.4 Local view
TYPES OF
CONVENTION PRACTICE
3. Aligned view
4. Enlarged view
5. Non-existing intersection line
6. Intersection : Hole on a cylinder
ALTERNATE POSITION OF
SIDE VIEW
ALTERNATE POSITION OF SIDE VIEW
Purposes
To save drawing space.
To improve the clarity of a drawing.
Conventional practice
Whenever the height of an object is small and the
depth is relatively large, places the side view beside
the top view.
Example
Top
Front
Right
Example
New orientation of views still
agree with 3rd angle system.
Slot becomes
more readable.
Hole becomes
more readable.
INCOMPLETED SIDE VIEW
DEFINITION
Incompleted side views are side views that
are eliminated a feature that can not clearly
seen from a selected viewing direction.
Example : Strictly orthographic projection.
Left-side view
Principal view
Right-side view
Details are interfered by those
on the opposite view.
Difficult to read and to dimension.
Example : Incompleted side views
Incompleted
left-side view
Principal view
Incompleted
right-side view
Better describe an object and
facilitate dimensioning.
Example : Incompleted side views representation
Principal view
PARTIAL VIEW
HALF VIEW
LOCAL VIEW
DEFINITION
Partial view is a view that represents portions
of the part that have a features need to clarify.
Half view is a partial view that is illustrated only
half of the part.
Local view is a view that shows only features
need to clarify.
Example : Partial views
Clearly seen
a shape.
Example : Half view
Left half
Right half
Center line acts as a
line of symmetry.
No continuous line !
Symmetry symbol
Thin line
(4H)
Example : Half view : alternative representation
Half view can be made by drawing the views
slightly beyond the line of symmetry.
No symmetry
symbol.
It is allow for writing
a break line.
Thin line
(4H)
In this course, we
omit the break line.
Example : Half view : two symmetry axes
Example : Local view
7
Shape of the
slot is completely
shown.
R6
Easy for
dimensioning
ALIGNED VIEW
DEFINITION
Align view is a view that is drawn by imaginarily
rotating the object’s features, appeared in a
principle view about symmetry axis.
Example : Necessity of align view
Strictly Projection
Apply
convention
Confuse
Waste of time
Clear
CONVENTION PRACTICE
For an object that has symmetrical positioned
features, it is advisable to show them on adjacent
view in true size at true radial distance from
the symmetry axis.
Example : Align view of holes
Given
Apply
aligned
convention
Gives the impression that there
is a hole at the center of the plate.
Example : Align view of holes
Given
Apply
aligned
convention
Gives the impression that holes
are at unsymmetrical position.
Example : Align view of holes
Apply
aligned
convention
Example
Example : : Align view of ribs
Apply
aligned
convention
Example : Align view of ribs & holes
Apply
aligned
convention
Example : Align view of ribs & holes & keyway
Make Orthographic Projection
Apply Convention
Example : Align view
ENLARGED VIEW
DEFINITION
Enlarged view is a view partly selected from
full view and is drawn with a larger scale.
Conventional practice
At full view, the selected portion is framed by
continuous thin line and having a name.
For an enlarged view, it must be specified both
name and scale used.
Example : Enlarged view
Full view
Enlarged view
or
A
Reference
position
A (3:1)
A (3:1)
Scale
NON-EXISTING LINE OF
INTERSECTION
DEFINITION
Non-existing line of intersection is the line of
intersecting surfaces that are eliminated by fillets
and rounds.
Conventional practice
When true projection mislead the representation
of an object, it is necessary to show the additional
lines that are projected from the actual intersection
of the surfaces as if the fillets and rounds were
not present.
Example : Non-existing line of intersection
Object does not has
rounds and fillets
Edges of the surfaces
are shown as lines in
the top view.
Example : Non-existing line of intersection
Object has
rounds and fillets
The view looks like a plate
with a hole !!
Convention practice required !
Construct a non-existing line of
intersection.
No edge !
(No intersection between surfaces)
Example : Non-existing line of intersection
INTERSECTION BETWEEN
FILLET AND ROUND
Runout
INTERSECTION BETWEEN
FILLET AND ROUND
TO DRAW A RUNOUT
R
R
R/3
Tangent point
about 1/8 of circle
R = radius of fillet or round
INTERSECTION BETWEEN
ROUND PLANE SURFACE
INTERSECTION
HOLE IN CYLINDER
Large hole : True projection
HOLE IN CYLINDER
Large hole : True projection
Small hole : Convention
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